The second stage of anesthetic induction is called delerium, because prior to cessation of breathing, the patient (sic) has a brief (few seconds) moment of skeletal muscle contraction and some tremulousness that can be mistaken for an awake response. In theory backed by experience, the person is already unconscious. This is followed by cessation of breathing as the diaphragm is paralyzed by the pancuronium (brand name Pancuron). It is this moment that the potential for an awakening is most undesirable and possible, especially if the Pentothal wears off or has not been properly absorbed. To be awake and not be able to breathe is probably one of the most terrifying sensations that a human can experience. Remember, the Pentothal and Pancuron are VERY short acting (maybe around 10 minutes if you don't check vitals and redose as needed). The effects of the potassium chloride (KCl) are more "permanent". Once the heart stops, loss of conciousness (LOC) occurs within seconds due to lack of perfusion of the cerebral cortex, where our supposed "higher" functions reside, though this practice contradicts THAT theory, eh?  

Many of the condemned have difficult IV acccess, due to addiction, etc. which can cause extravasation (leakage) of IV medications into the surrounding tissues instead of into the vein (also a complication of poor technique). This nearly eliminates the drug's effectiveness, irregardless of the dosage. I do not know if this happened in any of the executions that have occurred, but you need an experienced person to ID it.

So technically it is possible (obviously since this is the MO of general anesthesia-without the potassium), but as you say, not anywhere near the ballpark of dignified, or moral.

new lethal injection execution procedures they say "will result in the dignified end of life" for condemned inmates.

Can we say that the end of life for anyone who cannot accept their fate is dignified?  Would anyone consider being strapped to a gurney in front of witnesses who have come to see you invountarily euthanised 'dignified'?  I really struggle to follow their logic on that one, if there is any.

But that aside, I think that their decision to stick by the three drug protocol shows how unwilling they are to truly change.  The adjustments of the quantities of drugs make no sense to me.  (Although as a layman - even one with a special interest in this subject - maybe I'm missing something.  I'd love to hear Che's comments on this as he has much more knowledge in this area than I do.)  If the State is honestly satisfied that they can successfully sedate the inmate, then the pancuronium bromide is not necessary.  It is simply a cover-all for any mistakes and to keep anyone in the audience from unpleasant viewing (Heaven forbid).